New Delhi: In a breakthrough for farmers across the world, especially those from developing countries, scientists have discovered a way to clone hybrid seeds of rice.
Hybrid seeds created by crossing two varieties have superior qualities including high yield, pest resistance and climate tolerance and have been used by farmers for decades. However, a major challenge with such crops so far has been that unlike other crops, their seeds do not produce plants with same qualities.
So, farmers have had no option but to buy expensive hybrid seeds every year. “These seeds are not only expensive, but have to be purchased every year, which puts a lot of burden on poor farmers," said Jagmohan Singh, farmer union leader from Patiala, Punjab.
Now, scientists in the US and France have successfully tweaked a hybrid variety of Rice Japonica (Asian variety) so that some of the plants produce cloned seeds, according to research published in the latest edition of journal Nature. This, experts said, would enable farmers to re-plant seeds from their own hybrid plants and derive the benefits of high yields year after year, instead of having to purchase expensive new seeds every year.
Japonica and Indica are the two major varieties of rice grown around the world. While Japonica is grown in countries with cooler climates, Indica is usually cultivated in countries with hot temperatures such as India.
“It’s a very desirable goal that could change agriculture. The approach should work in other cereal crops, which have equivalent genes," said Prof Venkatesan Sundaresan of the University of California, Davis, who was among the researchers. Wheat, corn, barley and millets are among other cereal crops which have equivalent genes.
Asexual reproduction through seeds, called Apomixis, is known to occur naturally in more than 400 species of wild plants, but not in crops. This mechanism of seed production allows a plant to clone itself through a seed, without fertilization and, thus prevents any loss of hybrid characters in plants. However, recreating these pathways in crop plants has been a challenge to science.
“Ensuring that crops pass on hybrid qualities to seeds has been a major challenge, but the current research fills gaps in previous studies," said Imran Siddiqui, plant geneticist at the Centre for Cellular and Molecular Biology (CCMB), Hyderabad.
“The team has shown a proof of principle in an important crop like rice, which is very significant. The target now is to improve the efficiency of this clonal propagation to reap maximum benefit."
Researchers discovered that a rice gene called “Baby Boom 1" (BBM1) is expressed in sperm cells, but not in eggs. After fertilization, BBM1 is expressed in the fertilized cell. Scientists reasoned that this expression initially comes from the male contribution to the genome, and that BBM1 switches on the ability of a fertilized egg to form an embryo. The team then used gene-editing techniques to remove the ability of plants to undergo sexual reproduction. The egg cells are thus formed asexually.
“We are currently using over 40 hybrid varieties of rice in this country and the research would be very useful for farmers who would be able to save these seeds for future use," said V.P. Singh, former programme leader (rice) at Indian Agricultural Research Institute, whose team had once led a breakthrough in hybridization of Basmati rice following the development of PUSA-1121.
The current research was conducted by postdoctoral researcher Imtiyaz Khanday and Prof Venkatesan Sundaresan at University of California, Davis and researchers from the Iowa State University and INRA, France.